Lead-acid storage batteries have traditionally been manufactured by pasting lead alloy grids with battery makers lead oxide and then forming the positive and negative plates. The term "lead oxide" is used herein to include those oxides which are used by, and/or are familiar to, battery manufacturers, and usually include mixtures of lead oxides, typically the red and yellow oxides, with as much as 30% free lead. These oxides are mixed with other art-known ingredients such as expanders, bulkers, fibers, etc., to formulate particular pastes as is well known to those skilled in the art. Until recently, the grids have traditionally been cast from lead-antimony alloys, containing anywhere from about 4% to 12% antimony. The antimony in the cast grids makes the alloy more readily castable into sharp, thin sections and imparts mechanical strength to grids. Unfortunately, such antimony concentrations have a detrimental effect on battery performance to the extent that during cycling, the antimony corrodes away from the positive grids and deposits on the negative plates, where it lowers the hydrogen overvoltage and promotes gassing due to the electrochemical decomposition of the water in the electrolyte. Moreover, such amounts of antimony contribute to the tendency of the battery toward self-discharge. As a result, the industry has preferred to use the lower antimony content alloys and has long sought nonantimonial lead alloys as replacements for the antimonial lead. Included among such possible replacements are commercially pure lead, dispersion-strengthened lead, lead-calcium, lead-arsenic, lead-tellurium, lead-tin, lead-cadmium, lead-lithium and others. For purposes of this application, the term substantially nonantimonial lead is intended to include pure lead and those lead alloys which are so low (i.e., less than 0.5%) in antimony as not to be detrimental to the battery's performance. Of these non-antimonial alloys, lead-calcium alloys containing about 0.06% to about 0.09% by weight calcium are preferred.
While the non-antimonial lead alloy grids have substantially eliminated gassing and reduced self-discharge tendencies, positive plates made therefrom are short-lived when subjected to deep discharge cycling. In this regard, and by way of comparison, conventional cast lead-antimony positive grids will normally withstand 200 to 300 SAE deep cycles (SAE J537b), whereas the non-antimonials, i.e. lead-calcium, tend to fail after less than 80 cycles. The mode of failure of these plates lies principally in separation of the positive active material from the non-antimonial grid due to a loss of adhesion between the grid and the active materials. Loss of adhesion due to deep discharging is particularly undesirable in batteries used for golf carts, lift trucks, electric vehicles, etc., which all undergo deeper cycling than batteries used in automobiles equipped with alternators.